The instant invention relates to electrolytic reactors; it relates, more particularly, to sealed-volume reactors wherein two separate solution chambers are associated with the cathode and anode of the imposed electrical cirtuit, respectively, with the two chambers separated by a micro-porous septum.
The use of electrolytic cells for the treatment of electroactive species in a solution, such as removing metal contaminants from waste water, is known. For example, such a cell and a process are described in U.S. Pat. No. 4,308,122. That patent also describes the use of a diaphragm between the cathode and the anode of the cell, the diaphragm inhibiting fluid mixing from the region of the cathode to the region of the anode, but permitting passage of ionic species through it.
A problem with prior art cells is that they are relatively inefficient in removing small concentrations of metal from large volumes of solvent. When removing metal from solutions containing low concentrations of the metal, typically a deficiency of metal ion exists at the interface between the cathode and the electrolyte. This condition is described as Concentration Polarization and the layer around the cathode where this condition exists is called the Nernst layer. Removal of the metal from the solution is controlled by the rate by which the metal ions can diffuse to the cathode.
Other prior-art devices rely on the increased mass transfer rates made possible by the application of fluidized-bed principles, with masses of small, electrically conductive bodies suspended in the electrolyte and in periodic contact with an electrode. In such devices increased surface concentrations are achieved at the expense of low charge transfer rates induced by the intermittency of the electrical contact of the fluidized-bed particles with the current source.
Thus, it is apparent that there is a need for an electrolytic cell which is capable of continuously removing metals from large quantities of solutions, where the solutions contain only relatively small concentrations of metal ions, i.e., in the order of less than 500 ppm (parts per million).
There is also a need, increasingly motivated by environmental concerns and by the ever-increasing cost of disposing of even small amounts of many metals, of reactors capable of intermittent reversible operation; or the performance, simultaneously, of different chemical treatment pocesses in separate treatment chambers; for the modification of solute comlexes; the destruction of chemical species, such as cyanides, which are harmful or even poisonous; and other electrochemical processes in reactors of small physical size which can be operated at high currents and at relatively low drive potentials.